fix(server): echo requested URI in not-found data

Author: mattzcarey

.changeset/sep-2164-resource-not-found-invalid-params.md

@@ -7,4 +7,6 @@
 Resource not found now returns `-32602` (Invalid params) per SEP-2164; `-32002` (`ProtocolErrorCode.ResourceNotFound`) is deprecated. The error includes the requested URI in `data.uri` so clients can still distinguish not-found from other invalid-params errors. Clients SHOULD
 continue to accept legacy `-32002` from older servers.
 
+This supersedes the earlier 2.0.0-alpha.1 / #1389 resource error-code change that moved unknown resource reads to `-32002`.
+
 `NodeStreamableHTTPServerTransport` now forwards server-configured supported protocol versions to the underlying web-standard transport, so custom version lists passed to `McpServer` are also honored by HTTP header validation.

packages/server/src/server/mcp.ts

@@ -428,7 +428,7 @@ export class McpServer {
 
             // SEP-2164: nonexistent resources MUST return -32602 (Invalid params); the
             // requested URI is included in `data` so clients can distinguish not-found.
-            throw new ProtocolError(ProtocolErrorCode.InvalidParams, `Resource ${uri} not found`, { uri: uri.toString() });
+            throw new ProtocolError(ProtocolErrorCode.InvalidParams, `Resource ${uri} not found`, { uri: request.params.uri });
         });
 
         this._resourceHandlersInitialized = true;

test/integration/test/server/mcp.test.ts

@@ -2741,6 +2741,43 @@ describe('Zod v4', () => {
             });
         });
 
+        test('should echo the exact requested URI for nonexistent resources', async () => {
+            const mcpServer = new McpServer({
+                name: 'test server',
+                version: '1.0'
+            });
+            const client = new Client({
+                name: 'test client',
+                version: '1.0'
+            });
+            const requestedUri = 'HTTP://example.com:80/docs/../missing file.txt';
+            mcpServer.registerResource('test', 'test://resource', {}, async () => ({
+                contents: [
+                    {
+                        uri: 'test://resource',
+                        text: 'Test content'
+                    }
+                ]
+            }));
+
+            const [clientTransport, serverTransport] = InMemoryTransport.createLinkedPair();
+
+            await Promise.all([client.connect(clientTransport), mcpServer.server.connect(serverTransport)]);
+
+            await expect(
+                client.request({
+                    method: 'resources/read',
+                    params: {
+                        uri: requestedUri
+                    }
+                })
+            ).rejects.toMatchObject({
+                code: ProtocolErrorCode.InvalidParams,
+                message: expect.stringContaining('not found'),
+                data: { uri: requestedUri }
+            });
+        });
+
         /***
          * Test: ProtocolError for Disabled Resource
          */